Patent GB-477956-A (GB)
Title: Improvements in or relating to the manufacture of charges and cartridges for the generation of gas pressures
IPC: B01J7/00
Filed: 1936-07-06
Abstract: 477,956. Self-combustible charges for generating gases under pressure. HOLM, J. M., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. July 6, 1936, No. 18779. [Classes 9 (i) and 9 (ii)] A composite charge or cartridge for the slow generation of gas pressure and suitable for the actuation of mechanical devices, such as engine starters, fire extinguishers, pneumatic tools and motor-car jacks, comprises at least one element incapable of supporting its own combustion when ignited locally at atmospheric pressure by means ineffective to heat the whole element substantially above atmospheric temperature but nevertheless capable of supporting its own combustion when ignited under a pressure considerably in excess of atmospheric, said element comprising compacted nitroguanidine. The nitroguanidine is optionally employed in admixture with a binding agent, such as guanidine nitrate, cellulose derivatives, hydrocarbons, waxes, resins, gums, carbohydrates, fats &c., which, by virtue of its nature or proportion is incapable of causing appreciable deposition of free carbon under the operating conditions. The charge or cartridge also includes means for generating a pressure substantially in excess of atmospheric and sufficient to permit of the self-supporting combustion of the charge con. taining nitroguanidine. Such means may consist of a single unit of cordite or alternatively it may consist of a composite progressive train of charge elements as described in Specification 454,091. The charge elements, which are in the form of solid cylindrical pellets, are loaded into a standard unlined 12-bore paper shotgun case having a standard percussion cap with the most easily ignited elements next the percussion cap and the remainder in order of increasing minimum ignition pressure. According to one example, the gas-generating elements conveying the ignition to the characteristic charge element consist of a priming charge of Schultze Powder and a disc of Ardeer Cordite. In conjunction with this system, a single charge element is employed consisting of a compacted pellet of a 100 : 5 nitroguanidine : nitrocellulose composition. The nitrocellulose is mixed with the finely divided nitroguanidine in the form of a solution in acetone and, after the dough has been thoroughly incorporated, it is compressed into pellets in a die. The bulk of the acetone is subsequently eliminated by drying the pellets for a few days in an oven at 35-45‹ C. In a modification of this example, three further charge elements consisting of nitroguanidine, guanidine nitrate and gelatinised nitrocellulose in various proportions are employed. According to a further example, a single characteristic charge element consisting of a compacted pellet of a 100: 5 nitroguanidine : acetonesoluble cellulose acetate composition is used whilst in a modification of this example two further charge elements are added. consisting of nitroguanidine, guanidine nitrate and acetone. soluble cellulose acetate in different proportions. In a further example, a single characteristic charge element of a 100 : 2.5 nitroguanidine : gum-tragacanth composition is used whilst in a still further example two characteristic charge elements are employed, the first consisting of nitroguanidine compacted with 2¢ per cent of its weight of a resinous material containing polymerized methyl methacrylate and dibutyl phthalate in the proportion 90 : 10, whilst the second consists of a pressure-compacted mixture of equal weights of finely divided nitroguanidine and guanidine nitrate. In place of the nitrocellulose, there may be used nitrostarch, nitrodextrin or nitroalgin.